GENERAL PHYSIOLOGY OF THE CEREBRUM. 



183 



of organs, not completely separated one from the other as taught 

 by Gall, but intimately associated and to a certain extent dependent 

 one on another for their full functional importance. 



The Motor Area. The first experiments of Fritsch and Hitzig 

 disclosed the location of a cortical region in the dog which upon 

 stimulation gave definite movements. The later experiments of 

 Ferrier, Schafer, Horsley, and Beevor, particularly upon the apes, 

 gave reason for believing that this motor area surrounds the fissure, 

 of Rolando and extends inward upon the mesial surface of the cere- 

 brum. Its exact boundaries marked out by careful stimulation of 



Eyelid / Closure 

 Nose 



Fig. 83. Location of motor areas in brain of chimpanzee. (Sherrington and Green- 

 baum.) The extent of the motor areas is indicated by stippling; it lies entirely in front 

 of the fissure of Rolando (sulcus centralis). Much of the motor area is hidden in the sulci. 

 The regions marked eyes indicate the areas whose stimulation gives conjugate movements 

 of the eyeballs. It is doubtful, however, whether these represent motor areas proper. 



the region in monkeys was more or less verified upon man, since in 

 operations upon the brain it was often necessary to stimulate the cor- 

 tex in order to localize a given motor area. By these means charts 

 have been made showing the cortical area for the musculature of each 

 part of the body. The location of these areas as usually given is 

 represented, for the human brain, by Fig. 82. It will be seen that in 

 general the distribution of the areas along the fissure of Rolando 

 follows the order of the cranial and spinal nerves. Within each 

 area smaller centers may be located by careful stimulation; thus, 

 the hand and arm area may be subdivided into centers for the 

 wrist, fingers, thumb, etc. More recently Sherrington and Green- 



